Automatic telephone exchange



May 27, 1924.

F. A. LUNDQUIST AUTOMATIC TELEPHONE EXCHANGE Filed Sept. 27

May 27, 19 24.

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F. A. LUNDQUIST AUTOMATIC TELEPHONE EXCHANGE Filed Sept. 27. 1919 8 Sheets-Sheet 5 May 27, 1921. v 1,495,755

F. A. LUNDQUIST AUTQMATIC TELEPHONE EXCHANGE Filed Sept. 27, 1919 8 Shets-Shet 4 l l l, l 1 I i J I I l I l l May 27 1924. 1,495,755

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F. A. LUNDQUIST AUTOMATIC TELEPHONE E XCHANGE Filed Sent. 27. 1919 8 Sheets-Sheet a Patented May 27, 1924.

UNITED STATES 1,495,755 PATENT OFFICE.

FRANK A. LUNDQUIST, OF CHICAGO, ILLINOIS, ASSIGNOB, BY MESNE ASSIGNMENTS, 'ro HENRY S. CONRAD, TRUSTEE.

AUTOIATIC TELEPHONE EXCHANGE.

Application filed September 27, 1819. Serial No. 326,873.

To all 'TIJhOIIZ- it may concern;

Be it known that I, FRANK A. LUNDQUIST, a citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Exchanges, of which the followin is a specification.

1y invention relates to automatic telephone exchanges and has for its object improvements ,in the construction and operation of such exchanges.

In the accompanying drawings Fig. 1 represents two line switches with connections which extend in one direction to their associated local stations, and the other direction to selectors;

Fig. 2 is a diagram of two selectors which have connections to line switches on one side and connectors on the other;

Fig. 3 is a diagram of two connectors with their connections to selectors and line switches;

Figs. 1, 2 and 3 taken together constitute a diagram of the exchange;

Fig. 4 is a side elevation of the selector;

Fig. 5 is a side elevation of the connector;

Fig. 6 is an end elevation of the selector in the direction 6 of Fig. 4;

Figs. 7 and 8. are sections on lines 77 and 88, respectively, of Fig. 4;

Fig. 9 is a part of the selector viewed in the direction opposite to that of Fig. 4;

Fig. 10 is an end elevation in the direction 10 of Fig. 4, with some of the parts removed;

Fig. 11 is an elevation of the principal parts of the connector in the direction opposite to. that shown in Fig. 5; and

Fig. 12 is a section on line 1212 of Figs. 5 and 11.

Referring to Fig. 1, the part 20 is a pneumatic motor of the type shown and described designated by reference to the movablev part 20. r c

On one side of the motor 20 are two sets In this construction, the part' of ratchet teeth 22 and 23, which face in opposite directions. Adjacent to the upper end of the motor is a magnet 24 which is supported in any convenient manner on a frame work, not shown. The armature 25 .has a pawl 26 thereon which is adapted to gravity as long as such engagement is maintamed.

Near the magnet 24 is an air valve 28 of F the kind shown and described in my pending application Serial Number 244,731, filed July 13, 1918. This valve is in the nature of a check valve which is automatically closed by the pressure of the air in the supply pipe 29. The valve, however, has a projecting stem 30 which is engaged by the armature 25 or a projection thereon to opensaid valve, whenever the magnet 24 is energized, and permit air to flow from the supply pipe 29 thru the pipe 31 to the short stroke motor 32 to shift the adjacent contact springs. The motor 32 is in the nature of a compound diagram, and is known to the trade as a sylphon. It has a short axial movement and is slow to return.

In the apparatus hereinafter described there will be several motors of the general character of 20, several valves similar to 28, and several sylphons similar to 32. The descriptions given for these will serve for the others.

Supported adjacent to the sylphon 32, and operated by it is a lever 200 which has its other end operating upon a cam surface on the pawl 27. When the sylphon operates it moves the lever 200, and that in turn throws the pawl 27 into engagement with teeth 22 to hold the motor 20 in elevated position after air is exhausted from said motor.

Supported at a convenient place is a magnet 33 having ,two windings and an arma- Figs. 2, 4, 6, 7, 8, 9 and 10. This apparatus is for the purpose of moving certain wipers, insulatingly supported on a cross-head 36, first horizontally and then vertically to complete electrical connections from a line switch to a connector. The various parts pf the selector are supported directly, or by means of brackets, on the frame 37.

At the right in Fig. 4 is a. magnet having the windings 38 and 39, and armatures 40 and 41. The armature 40 is a light one and is moved toward its retracted position by a spring 42. The armature 41 is a heavy one and is moved toward its attracted position by a spring 43. Over the armature 40 is a valve 44, the projecting stem of which bears against the upper face of the armature 40 or a projection thereon. The air pressure in the pipe leading to this valve 44 causes it to press the armature 40 toward its attracted position, but the sprin 42 has a force a little greater than that o the airy pressure so that when no current flows thru the coil 38, the spring 42 will open valve '44. However, there is a mechanical device which normally holds the armature 40/ in attracted position and slightl removed from the projecting pin of va ve 44. This device is shown diagrammatically in Fig. 2 as a T- shaped part 45 acted upon by a spring 46 but normally held in the position shown b a bell crank 47 pivoted at 63, which bel crank is connected tor a motor to'be later described. 7

Over the armature 41 is a valve .49, the stem of which acts upon the armature to move it downward to its retracted position. The force of the spring 43 is slightly less than the force of the air in the supply pipe acting to close valve 49. As a consequence, the valve 49 normally holds .the armature 41 in its retracted position as shown at the left in Fig. 2. Fig. 4 shows the attracted position. As a' consequence of the construction described, rapid impulses flowing thru the magnet 3839 will cause the armature 41 to remain attracted while the armature 40 responds to the impulses. .The reason why the armature 41 remains attracted is because the force of the air on valve 49 is so mature that said force does not have time to overcome the inertia and retract thearmature in the brief interval from one impulse to the next.

Located in the lower part of the frame 37 is a motor 50 provided with a rod 51 which extends upward and connects to the bellcrank 47 (Fig. 2). When the valve 49 is opened, compressed air flows from the supply 1pipe to the motor 50 to remove bellcran 47 from part 45, and also to close certain contact springs to be described later. The removal of the bellcrank 47 permits the part 45 to release the armature 40 and also to open an adjacent valve 52. Thevalve 52 admits air to the horizontal motor 53 which operating thru suitable connections, puts a strain upon the carriage to move it toward the right as shown in Fig. 4, and towards the left as shown in Fig. 2.

Extending across the middle of the selector between the upright parts of the frame 37 is a bar 54 which serves as a guide for the horizontally movable carriage 55. The carri'age 55 is a rectangular frame having two sets of ratchet teeth 56. Pivoted at 57 on the bar 54 is a. bellcrank'58, one arm of which terminates in a pawl 59 arranged to vibrate between the sets of teeth 56, and the other arm of which has a pin 60 resting in a slot in the end of a link 61. 61 connects to a motor 62 which is operated by air admitted by valve 44. F

Supported in the frame is a rock shaft 63 on which is a spring 64 acting to normally hold the shaft in the position shown in Figs. 4 and 8. Extending out from this shaft is an arm 65 which has its outer portion 66 bent around so that it lies parallel The link' with the shaft 63. The portion 66 is COD- "69 is released, and the pawl 59 is free to vibrate without restraint. This is a provision which permits the switch to release without too great a tension on the retractile spring 53 which acts against the motor 53.

Secured to the horizontally movable carriage is a vertical guide 7 Q, on which guide.

is a carriage 71 which carries the cross-head 36. Supported on a bracket 72 (Figs. 7 and 9) is a vertical motor 73 which is connected at 74 to the cross-head 36. When air is admitted to motor 7 3, the insulated wipers on the cross-head are moved upward.

On the'carriage 71 are ratchet racks 75 and 76, the'teeth of which face in opposite directions. On the carriage 55 is a pawl 77 arranged to engage the teeth 7 5. When the motor 50 is in its lower position, the part 66 carried on the rock sha 63 strikes the tall 78 of pawl 77 to hold said pawl away from teeth 75. But when the motor 50 operates, the pawl 77 is permitted to fall into the teeth 75 as soon as the carriage 71 moves upward. On the uide 70 is a pawl 79 arranged to engage t e teeth 76.. The manner of controlling pawl 79 will be described hereinafter. V i

Adjacent to the shaft 63 is another rock shaft 80, on which is secured the armature 81 of magnet 82. On the carriage 55 isa proleft as shown in Fig. 4, the roller 83 engages the cam 84 so as to rock the shaft 80 in a direction which moves the armature 81 to its attracted position. When the carriage 55 moves from its normal position, the roller 83 leaves the cam 84 and permits shaft 80 to .rock in the opposite direction. On the shaft 80 is a bail 85 which lies under the tail of the pawl 79. When the armature 81 is in its attracted position, the pawl 79 engages teeth 76 to restrain carriage 71 from upward movement, but when armature 81 falls back, the bail 85 also falls back and permits pawl 79 to clear the teeth 76. d

On a convenient bracket is a motor 86 (Figs. 4 and 8) which has a collar 87 on it, and projecting downward from the shaft 80 is an arm 88 arranged to be engaged by said collar when the motor 86 is operated. When such engagement occurs, the shaft 80 is held so as to retain the armature 81 in its attracted position, even after the roller 83rhas been removed from the cam 84.

The motor 86 is shown with a conical or bullet-shaped head. The form of the head has nothing to do with its operation, but is here adopted as an arbitrary form to indicate a slow motor. By that I mean a motor which is connected to a pipe which receives air pulsations, but which motor does not respond to such pulsations. This result is accomplished by restricting the size of the exhaust outlet so that the air which enters the motor to cause it to rise does not have time to escape during the brief interval from one pulsation to the next. The slow motor corresponds to what is well known as a slow relay in telephone exchanges.

On the shaft 80 near the magnet 82 is a projection 89 which extends under the projecting stem of a valve 90. \Vhen the armature 81 of magnet 82 is in its attracted position, the projection 89 is clear of the valve stem and the valve 90 is in closed position. But when the armature 81 falls back, the projection 89 opens the valve 90 to permit compressed air to the sylphon 91, and to the motor 73.

In the lower part of the frame is a shaft 92 which has on it a spring 93 and a bail 94. On the lower end 0 the carriage 71 is a roller 95 which rests on the bail 94 and holds the shaft 92 against the turning action of the spring. This holding by the roller 95 contmues while the carriage is moving horizontally, 'as will be described later, but as soon as the carria e 71 is elevated by the motor 73, the she. turns to raise the bail 94. In Fig. 2, the roller is represented by a projection 95 bearing on another projection 94, on shaft. 92.

, On the end of the shaft 92 is an arm 96 which connects to a vertically movable rod 97 having a slot 98 in its upper end. This slot embraces a pin 99 (Figs. 4 and 10) in the horizontal arm of the part 45. The vertical arm of the part 45 normally rests over a rojection 100 secured on the armature 40. T e part which is represented as a bellcrank 47 in the diagram, is the arm 47 on the shaft 63. See Figs. 4 and 10.

On the shaft 80 is an upwardly projecting arm 101 (Figs. 4 and 8), and pivoted on the frame at 102 is a catch 103 designed to engage and hold the arm 101, and consequently the shaft 80, under certain conditions. The catch 103 has a tail piece 104 which extends adjacent to the rods 51 and 97. On rod 51 is a hook 105, and on the rod 97 is a projection 106, both of which extend over the tail iece104. If either of said rods is in its ower position, then the catch 103 is. held away from the arm 101. But if both rod 51 and rod 97 have been elevated, then catch 103 is free to engage and hold arm 101 if shaft 80 has been rocked in the meantime.

On the selector are various contact springs, the character and purpose of which will be made evident in the description of the operation. On the cross-head 36 are insulated wipers which make electrical connection with certain bank contacts. These bank contacts are shown in transverse section in Fig. 9, and in side elevation in Fig. 2. They are of the same character as those shown in Fig. 1. Further description of the structure, and of the air connections to motors and valves will be given in the description of the operation.

The connector shown in Figs. 3, 5, 11 and 12 has many structural features similar to those of the selector, and hence the description may be somewhat brief. In the frame 110 is supported mechanism for moving certain wipers which are supported on but insulated from a cross-head 111.

At the left in Fig. 5 is a magnet having windings 112 and 113, and armatu res 114 and 115 which act upon valves 116 and 117. These parts are similar to those in the selector and serve to admit air to the motor 118 which acts upon bail 119 to rotate shaft 120.

riage 124, and on this carriage is a vertical bar 125 which serves as a guide for the carriage 126 to which is secured the cross-head In the frame is a motor 127 which operates thru link 128 and lever 129 to put a strain upon-the carriage 124 to move it to the left as shown in Fig. 5 and to the right as shown in Fig. 11. Movement in this direction is restrained by a pawl 130 pivoted on the bar 123 and held in engagement with the lower-teeth of the carriage 124 by a spring 131. The pawl 130 has a tail piece 132 which projects adjacent to the teeth on the bar 122, but is not normally in engagement with said teeth.

On the stationary part of the motor 121 is a clock spring 133, and adjacent to this spring is a rotatable disk 134 having certain ratchet teeth therein. On the disk is anarm 135 which bears against an arm 136 on shaft 120. The spring 133 holds the disk 134 in such a position as to keep arm 135 against arm/136, and thenormal position of 7 parts 134, and 122 is determined by the normal position of shaft 120. But when motor 118 rotates shaft 120, it rotates disk 134, motor 121 and bar 122 against the action of spring 133. P p

On the disk 134 is a pin 137, and on the cap part of the motor 121 is a collar-.138 having a slot which embraces the pin 137. This connection causes disk 134 and motor 121 to rotate together, but permits said motor to slide axially with respect to the disk.

" On a shaft 139 is an arm 140which bears against the pin 137, and also on shaft 139 is an arm 141 which projects under the normally closed valve 142. When the motor 118 operates to rotate the various parts described, it causes arm 141 to open valve 142 andadmit compressed air to the motor 127.

Pivoted at 143 on the frame is an arm 144 which extends upward and engages the arm 136 by reason of the action of a spring 145 on the pivot 143. On the arm 144 is a pawl 146 ad acent to disk 134. When the arm 136 is in its normal position the pawl 146 is held out of engagement with the disk 134 when said-disk is rotated. But when the arm 136 is moved by the motor 118, the pawl 146 ispermitted to engage the disk 134.

Supported on asuitable bracket is a motor 147, and supported on the .frame is a slide 148 which has a projection 149 extending over the top of motor 147. Pivoted to the slide 148 is a pawl 150 which lies adjacent to the disk 134.. On the pawl 150 is a tail.

vertically reciprocated without affecting the disk 134, but if the shaft 120 is in rotated position by reason of action of motor 118, then a downward movement of slide 148 will cause pawl 150 to engage the teeth of disk 134 and turn it. This downward movement is by a spring 153 shown in the diagram of Fig. 3 but is omitted from the other views. Pivoted at 154 (Fig. 11) on the guide 125 is a T-shaped lever 155. On'the ends of the head of the T are pawls 156 arranged to engage the ratchet teeth on the slide or carriage 126. Pivoted at 157 on the guide 125 is a lever 158 having two arms, one of which has a fork 159 which embraces the bail 11.9. The ends of the arms of lever 158 are cam shaped and engage pins on the pawls 156 to normally hold said pawls from engagement with the teeth of carriage 126. But when the motor 118 operates to move bail 119, the lever 158 is moved so as to permit the pawls to engage the ratchet teeth on the carriage. If the T 155 be then vibrated on its pivot 157, the pawls 156 will operate on the ratchetteeth to elevate the carriage 126 step by step. In this operation. each movement of the Tfrom its midposition causes a half step of the carriage 126, and a complete stepis produced by a complete vibration.

When the slide 148 falls after being raised by motor 147 the pawl 150 engages a tooth on the disk 134 to give said disk a partial rotation. Such rotary movement turns the bar 122 so that the tail 132 of pwal 130 enters a space between two teeth on said bar. If the motor 121 be then reciprocated, the pawl 130 will be vibrated between the upper and lower teeth of the carriage 124. If this occurs when air pressure is on the motor 127, this vibrationjof pawl 430 will act as an escapementto permit carriage 124 to move step by step from its normal position.

lf after such horizontal movement, the slide 148 be given another reciprocation, then the bar 122 will be moved another step from engagement with tail piece 132 to en- 163 for the T 155. There are also certain other retractile springs, the purpose of which will be evident from an inspection of the drawings.

motors and levers. the purpose of which will become evident from the description of the operation. On both-selectors and connectors. four wipers are shown, but in the present electrical arrangement of exchange, only three of them are functional.

In describing the operation of the exchange it will be assumed that a call 1s being made thru the line switch shown at the left in Fig. -1. This switch is provided wlth wires 170 and 171 leading to a local station.

- selector.

In making-a call. the subscriber at the local station connects lines 170 and 171 together, whereupon a circuit is completed as follows: battery X-upper winding of 33172-- 173 174 '171 170 175175175" lower winding-grdund-X.

This causes magnet 33 to attract its armature 34 to open valve 35 and to close springs 180 and 181. Opening valve 35 admits air to motor 20 which immediately rises carrying its wipers on a trunk hunting movement over the bank contacts shown above them. \Vhen thewviper 179 reaches a contact which has a groiind connection, as for example thru the wire 178, a circuit is completed as follows: ground at the left in'Fig. 2176 177178-17918224183180 181 186184-184185battery and ground.

This operates magnet 24 to throw pawl 26 into the ratchet teeth 23 to stop the upward movement of the motor 20 with its wipers on the terminals of the found trunk. The attraction of the armature 25 by the magnet 24 also opens the valve 28 to permit compressed air to the sylphon 32. The operation of this sylphon shifts the adjacent contact springs to their alternative position, and also moves the lever 200 to throw the pawl 27 into teeth 22 and to close spring 187 and 188. Vhen the sylphon 32 shifted the adjacent contact springs it broke the circuit for magnet 33 at 174 and 175, and at the same time connecting these springs to other springs for completing a circuit thru to the When the circuit is broken for magnet 33, the armature 34 falls back to break the circuit for magnet 24. But the lGVQlQOO previously closed springs 187 and 188 so that the circuit is maintained by the branch from 183 by way of 188187- l87184184-2O2Cgr0und.

'hen the armature 34.falls back it permits valve 35 to close, with the result thaf air becomes exhausted in motor 20. The

pawl 27 however, holds the motor 20 against falling. and will continue to hold it as long as the sylphon 32 continues to receive air thru valve 28.

The operations just described result in connecting the calling station to an idle selector by a circuit as follows: 170-175- 189 190 wiper 191 192 -19338 ground battery B 39194195-196- 197199174171-local station.

The current from the battery B over this circuit causes-the magnet 38-39 to attract its armatures 40 and 41. The armature 40 -is normally retained in its attracted position so nothing occurs at this point at this time. but the attraction of armature 41 opens I valve 49 to permit air to flow from a source thru pipe 201 to motor 50. The other branches of this pipe are at this time closed by valves 44 and 90.

The operation of motor 50 shifts spring 177 from a ground connection to battery A,

but just before this occurs, the sylphon 32 shifted the spring 184 from a battery connection to a ground connection thru'spring 202. The result of this is that the magnet 24 of the line switch now receives its current from battery A at the selector switch instead of from battery at the line switch.

The motor 50 also shifts the bellcrank 47 to permit spring 46 to move the T 45 to both release armature 40 and to open valve 52. The armature '40 at this time remains attracted by reason of the current thru magnet 3839, but opening the valve 52 permits compressed air to flow thru pipe 203 to motor 53. This puts a horizontal strain on carrlage 55 to move it, and consequently the wipers of the selector, toward the left as shown in Fig. 2.

The operations so far described are automatic ones which occur as the result of a subscriber closing electrical connection at his station between wires 170 and 171. To recapitulate these operations briefly, circuit is completed thru magnet 33 which opens valves 35-and permits motor 20 to move its wipers over a series of bank contacts. When contacts are reached which represent an idle selector, a current flows thru magnet 24 to stop motor 20 'and shift the local station connections from magnet 33 on the line switch to magnet 3839 on the found selector. This cuts out magnet 33 and causes motor 50 to change certain mechanical and electrical connections, and motor 53 to put a strain on the carriage 55.

The subscriber is presumed to have an ordinary calling'device at his local station, the operation of which breaks and then remakes the circuit a desired number of times. The rapidity with which the circuit is broken and remade is presumed to be too great to permit the slow armature 41 to fall back, so that the only things under immediate consideration are the responses of armature 40 to the impulses controlled by the calling device.

' Upon the first break and remake of the circuit thru magnet 38-39, the armature 40 is retracted and then attracted. In falling back, the armature 40 ens valve 44 and permits air to flow from plpe 201 thru pipe 204 to motors 62 and 86. Upon being iattracted again, ,air is cut oil from these mo tors. As the armature vibrates back and forth in response to the breaks and remakes of the circuit of the local station, air flows in "pulsations to the motors 62 and 86. The motor 62 responds to and moves with these pulsations, but the motor 86 is a slow motor and remains in its moved position durin tion of his calling device, he leaves the circuit closed thru the magnet 38 39. The

consequent attraction of the armature 40 cuts air from motor 86 long enough for it to. fall back from 88, which in turn ermits armature 81 of magnet 82 to fall bac This movement causes projection 89 to 0 en valve 90 and permit compressed air to ow from pipe 201 thru pipe 205 to motor 73 and sy phon 91. The motor 73 moves the carriage 71 upward, and the sylphon 91 shifts the adjacent contact springs.

The carria e 71 carries the wipers of the selector over ank contacts in a trunk hunting movement similar to that described for the line switch. When terminals are found which represent an idle connector, a circuit is completed as follows: ground D at the left in Fig. 3-206-207-208209 to Fig. 2-:210-21121282-213214215battery A. The consequent operation of magnet 82 turns shaft to permit valve to close and cut air from motor 73 and sylphon 91. Turning the shaft 80 causes the bail 85, see Fig.v 4, to throw the pawl 79 into engagement with ratchet teeth 76 and stop the carriage 71 with its wipers on the terminals of the found trunk. As the current is on the magnet 3839 during this operation, air is on motor 50 and the arm 66 is free from the tail of. the pawl 77, see Fig. 4. As a consequence, the pawl 77 falls into engagement with the teeth 75 of carriage 71 and prevents that carriage from falling back when the air iscut off from motor 73.

As a result of the operations just described, the local station is connected to an idle connector by a circuit as follows: 170-- respond to such impulses but remains attracted until the break of the circuit thru the magnet is of longer duration than occurs in the ordinary operation of a calling device.

The motor 118 operates thru parts 119, 134 and 140 to open valve 142 and permit compressed air to flow to motor 127, which puts a horizontal strainupon the carriage 124. In this operation the disk 134 is advanced so as to bring one of its teeth nearer than before to the pawl 150. It also permits pawl 146 to engage with the disk 134.

The operations so far described are automatic ones consequent upon the selector finding an idle connector. When the subscriber again operates his calling device, the consequent vibrations of armature 114 open and close valve 116 to permitpulsations of air to flow fromspipe 231 thru pipe 232 to slow motor 233 and to the escapement motor 121. The motor 233 opens valve 234 to permit air to flow to motor 147, and keeps air on motor 147 as long as successive impulses flow thru magnet 112-113. The operation of motor 147 lifts rod- 148 and brings pawl 150 adjacent to the first tooth or notch in disk 134. It also shifts certain electrical connections to be described later.

The movement ofdisk 134 by 1uotor-118 turned the rack 122 to engagement with the tail 132 of the pawl 130 so that the pulsations going to motor 121 will operate said pawl to permit the carriage 124 to move under strain of motor 127. At the termination of the series of electrical impulses coming as the result of operating his calling device, the armature 114 remains in attracted position and the valve 116 closes. Closing valve 116 shuts air from motor 233 which in turn shuts air from motor 147 which falls back. This permits spring 153 to force rod 148 downward. In this movement, the pawl engages the disk 134 to advance it one 70 228196- 197-199 174-171 local again fall to advance the disk 134 another step which carries the rack 122 beyond and clear of the tail piece 161' of lever 155.

It willbe assumed that the connector stops on the upper bank contacts shown in Fig. 3,

and the wires leading from these contacts are the normal wires of the line switch shown at the right in Fi 1. At the time of coming to this position t e rod 148 is in elevated position, but as soon as there is a pause in the im ulses' which move the connector to its desired ition, the motor 147 and rod 148 fall bac whereupon a circuit is completed as follows: battery F at the left at the upper left hand parts of Fig. 3- 240--241242- -243*private wiper 244- 245-normal wire 246 to the line switch at the right in'Fig. 1-251179 182--24-183 -180--250 249 --248- -247- 252-ground.

This 0 rates the magnet 24 of the line switch be onging to the called station, which magnet throws pawl 26into the teeth on motor 20 to lock t e called line switch against displacement. The magnet 24 also opens its valve 28 to admit air to the syl hon 32 to shift adjacent contact-springs. on these things have been done, the complete circuit between the calling and called stations is as follows :calling station170 175189- 190191-192216227226225224 223-'22226i5264263.-262 261 normal wire 260 to Fig. 1-191-190-189- 175-170-called' station-171-174-199 197-259--normal wire 258 back to Fig. 3- 257-256-2'55-254-253-221-t0 Fig. 2-

220219218-217228195 to Fig. 1-

196-197-199-174171--calling station.

The signaling circuit is omitted to avoid complication, and because it is not necessary to a full understanding of the present invention. It may be an adaptation of well known devices to the present arrangement. The previous description assumed that the line switch of the called station was in its normal position. If, however, that line 'switch hasbeen moved from its normal position, then the terminals of the normal wires would be open and the calling switch would make no connection.

It was also assumed that the called station had not been previously called by some other party. If we assume that the connector at the right in Fig. 3 is in connection with the bank contact 245, 257 and 261 at the time the connector at the left comes to these contacts, then we would have two tion because air is on motor. 147 during switch movements. Under these conditions a circuit will be completed as follows :battery-F at the right240241242- 243 244-245 to 244 at the left-243-242-' 266-'- 267-268-269-270-271-gr0und.

Under these conditions the magnet 267 will cause its armature 272 to move the bellcrank 273 away from rod 148 so that when said rod falls it will not close the circuit fori-the wipers 262 and 256 at the adjacent contact springs. The bus signal which would result from this com ination is omitted for. the sake of simplicity, and because it is not necessary to an understanding of how connections are made from one station to another.

When the subscriber at the calling station han up his receiver he breaks the circuit at his station for the magnet 3839on the selector and magnet 112113 on the connector. This permits the armatures of these magnets to fall back. When armature 41 falls back, the valve 49 closes and shuts air from motor 50 which also falls back. This last shifts the adjacent springs and breaks the circuit for the magnet 24 on the line switch. This permits all of the parts of the line switch to return to normal position.

When the motor 50 falls back it releases the holding pawl 77 so that the carriage 71 may fall by gravity, and also releases the tension on spring 69 so that the carriage 55 will return to normal position under tension of spring 53". The other restoring actions on the selector will be readily understood by reference to the previous de scription of the mechanical construction.

When the armature 115 on the connector falls back, the valve 117' closes and shuts air from the motor 118 which also falls back. When the motor 118 returns to its normal position it releases the pawl 146 so that the disk 134 and associated parts return to normal position. It also moves the lever 158 to release awls 156 so that the carriage 126 may fa l. The other restoring actions of the connector will be understood from' the previous description.

When the connector falls back, the battery F at the upper left-hand part of Fig. 3 is disconnected from the magnet 24 of the line switch at the right of Fig. 1 by reason of the private wiper 244 leaving the bank contact 245. As a result of this, the moved parts of this line switch return to normal. position.

I will briefly review the operations. The subscriber removes his receiver, and the rising of his receiver hook closes connection switches on the same connection. At the between lines 170 and 171. This completes the connections, and a circuit is completed thru the magnet 3839 of the found selector. This operates thru intermediaries to put air pressure on the hprizontal motor 53.

All operations up to this point are automatic as the result of lifting the telephone receiver from its hook. Wheni the subscriber operates his calling device the first time he sends electrical impulses thru the magnet 383.9 and these are transformed into air pulses which reciprocate the motor 62 for operating the escapement a desired number of times. When there is a pause in these impulses, air is cut off from motors 53, 62 and 86, and is admitted to motor 73.

This starts the selector on a trunk huntingmovement, and the motor 73 in rising/removes the part 95 from the bail 94 so that the arm 96 may push the rod 97 upward to turn part on its pivot and thereby lock armature 40 against further vibration.

As soon as a trunk is found leading to an idle connector,'the selector is stopped and the local station connections are extended to the magnet 112113 on the found connector. This operates thru, intermediates to put air pressure on the horizontal motor 127.

When the subscriber again operates his calling device he sends electrical impulses thru magnet 38-39 and magnet 112-113. Those thru magnet 3839 are non-effective because armature 41 is slow and was in attracted position before the impulses started, and armature 40 is locked against operation by the part 45. But the impulses thru magnet 112 113 are transformed into air pulses which reciprocate the motor 121 to move the switch horizontally a desired number of steps by the operation of escape pawl 130. When there is a pause in these impulses, the rack 122 is shifted from pawl' 130 to the lever 155 which carries the driving pawls 156. When the subscriber again operates his calling device, the electrical impulses are again transformed into air pulses which reciprocate motor 121 to move the switch upward step by step.

When the final pause comes in the operation of the calling device, the motor 147 of the connector falls back to connect the calling station to the normal wires of the called station. In this operation a circuit is completed thru magnet 24 of the lineswitch belonging to the called station, and this results in the station being connected toits own normal wires. 5

During conversation current is maintained on magnets 3839 and 112113 .thru the calling station, on ma et 24 of the. calling station line switch y the selector, and on magnet 24 of the called staftion line switch by the connector. When the I the magnets 38 -39 and 112-113 can no lon er hold them in advanced position. In

falling back, the selector breaks the circuit on one, line switch, and the connector breaks it on the other. v

What I claim is:

1. In a selector, wipers,apneumatic motor for moving them, a restraining device for holding them against the action of the pneumatic motor, and a pneumatic devicev for vibrating the restraining device so that the wipers may be advanced step by step by the motor. A

2. In a selector, Lwipers, a pneumatic motor for moving them, a restraining device, a second pneumatic motor connected to the restraining device, a source'of' compressed air, a magnet, means by which upon a circuit being completed thru said magnet air will flow from the source to the,first motor, and means by which upon the circuit being interrupted so as to cause electrical impulses to flow thru said magnet air will be admitted to the second motor so as to cause it to make corresponding reciprocations.

3. In a telephone exchange, a selector having a magnet thereon, means by which upon the operation of some earlier switch as a line switch a circuit is completed thru said magnet, a power device brought into operation to move the selector when a cir cuit is so completed, an escapement serving to restrain such movement, a pneumatic motor for operating said escapement, and means for controlling said motor by impulses flowing thru said magnet.

4. In a telephone exchange in which calls are made from a, local station by connections extended thru a line switch, a selector and a connector; a starting magnet on each mechanism operated by a, connection made at a local station; means by which upon the line switch extending the connection to the magnet of the selector ,the magnet of the line switch will be cut from the connection; and means by which the selector extending the connection to the connector the magnet of the selector will be locked against operation.

5. In the electrically controlled and pneumatically operated mechanisms of a. telephone exchange, means for transforming a' series of electrical impulses into corresponding series of air pulsations, and mechanism moving devices operated step by step by escapements in response to. such pulsations.

6. In the electrically controlled and pneumatically operated mechanisms of a telephone exchange, means for transforming electrical impulses into correspondin pulsations, and escapements operated such pulsations.

7. In a telephone exchange, means for automatically selecting a trunk, a mechanism connected to such trunk, a pneumatic device for moving the mechanism," a source of compressedair, and means by which a series of electrical impulses flowing over the selected trunk will be transformed into corresponding air pulsations to operate the device for moving the mechanism to extend a connection. 4

8. In a telephone exchange, means for automatically selecting a trunk, a mechanism connected to such trunk, automatic means for putting a strain upon the mechpulses flowing thru said device cause *corresponding air pulsation to flow from said source to said motor to vibratesaid pawl. 10. A switching mechanism, a pneumatic motor as 121, a source of compressed air,

an electrical device, means by which a series of electrical impulses flowing thru said device cause a similar series of air pulsations to flow from the source to said motor to move the mechanism in one direction, and means by which a second series of electrical impulses flowing thru said device cause a similar series of air pulsations to flow from the source to said motor to move the mechanism in another direction.

11. A switching mechanism, a pneumatic motor for operating a device to move the mechanism in one direction and at another time for operating a device to move the mechanism in another direction, a source of compressed air for'o erating the motor, and means for causing t e air to flow from the source to the motor in a series of rapid pulsations.

12. A switching mechanism, devices for cause correspondin :pressed air,'a magnet, means by which electhe' mechanism in one direction,

trical impulses flowing thru said magnet air pulsations to flow from the source to t e motor for moving the mechanism, and means by which upon a pause occurring in the flow of impulses such pause will cause said motor to be shifted from one set of devices to the other.

13. In an automatic telephone exchange having selectors and connectors and means for the automatic selection of idle trunks, a magnet on each selector operated when a trunk is selected leading to such selector, a similarmagnet on each connector and operated in a similar way, and means for automatically locking the armature of the magnet on the selector at the time the trunk is selected to the connector.

14. In a telephone exchange in which successively selected trunks are connected to form parts of a complete circuit, a magnet connected to each section, and means for automatically locking the armature of a magnet on an intermediate section when the next trunk section is selected.

15. In a trunk selecting system having a switching mechanism on each trunk, means for putting a strain upon the mechanism when the associated trunk is selected, a spring actuated pawl serving to hold the mechanism from movement, and automatic means for varying the tension of the spring -on the pawl at different times in the operation of the mechanism.

16. In a switching mechanism,'a source of power for moving it, a'spring actuated holding pawl, and automatically operating means for varying the tension of such spring.

17. In an automatic trunk selecting operation between the line switch and selector of a telephone exchange, a motor for moving the line switch over contact terminals, a stopping magnet for arresting the movement of the line switch when it reaches the terminals of an idle selector, means for completin a circuit for the magnet from a bat terv t ru contacts closed on both line switch an selector, and automatically operating means for reversing the battery connections by shifting the contacts on both line switch and selector.

FRANK A. LUNDQUIST. 

